The development of new seed varieties is performed by selectively introducing desired characteristics into a plant population. The resultant seeds from the plant population are then examined to identify seeds to be used in further development of the plant variety. Often times a visual marker may be used to identify seeds for use in further development. An exemplary visual marker includes the presence or absence of a given color in the embryo region of the individual seeds. Visual markers may also be used in the identification of other types of plant materials. For example, the color of the root may be used to separate seedlings.
A visible genetic color marker in the corn seed is utilized in double haploid breeding to identify correctly pollinated seeds as well as putative haploid seeds. The male pollinator, or haploid inducer, confers the dark purple color exhibited in the fertilized seed endosperm by passing on the Navajo marker gene rnj. However, the absence of the genetic marker color in the embryo tissue within the seed indicates that no male genes entered the ovule nucleus, leaving the embryo with only one set of chromosomes inherited from the female parent.
Therefore, expression of the color marker in the endosperm tissue, but lack of expression in the embryo, indicates a putative haploid kernel (PHK) which is useful for breeding purposes. Color expression in both regions of the seed indicates a normal diploid kernel with genes from both the male and female parents which has no value for this type of maize breeding.
Current methods of separating PHK kernels from a seed lot is performed using human labor which is both time consuming and relatively expensive. In a typical seed lot about 10 percent of the seed lot are PHK kernels.